Overview

Comprehensive Description

Description

Dendrobates auratus can be identified by their calligraphic brillant green markings on a black background on their dorsal side (Caldwell and Summers 2003). Ventrally, they are marbled or spotted with yellow, blue, or green on dark background (Guyer and Donnelly 2005). Among populations there are variation in both hue (ranging from white to blue-green) and pattern (from thick stripes to dots) (Caldwell and Summers 2003). Dendrobates auratus has a smooth upper surface with a head that is relatively long. The snout truncates to slightly rounded (Savage 2002). Dendrobates auratus is the largest poison-dart frog in Costa Rica, with adult females ranging from 27.0-42.0 mm and adult males ranging from 25.0-39.5 mm (Leenders 2001).

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Range Description

This species occurs in the humid lowlands from southeastern Nicaragua on the Atlantic slope and southeastern Costa Rica on the Pacific versant to northwestern Colombia (Golfo de Uraba on the Caribbean coast and the lower Atrato River drainage and Bahia Solano on the Pacific coast) (sea level up to 1,000m asl). In 1932, 206 specimens of D. auratus from Taboga or Taboguilla Islands, Panama were released in the upper Manoa Valley, Oahu, Hawaii in an attempt to control non-native insects (Silverstone, 1975; McKeown, 1996). A few feral populations of D. auratus descended from these animals still persist in the mountains and valleys of Oahu.

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Global Range: Humid lowlands from southeastern Nicaragua on the Atlantic slope and southeastern Costa Rica on the Pacific versant to northwestern Colombia (sea level to 1,000 m asl). In 1932, 206 specimens of D. auratus from Taboga or Taboguilla Islands, Panama were released in the upper Manoa Valley, Oahu, Hawaii in an attempt to control non-native insects (Silverstone, 1975; McKeown, 1996). A few feral populations of D. auratus descended from these animals still persist in the mountains and valleys of Oahu.

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Distribution and Habitat

This species can be found on the Caribbean slopes from southern Nicaragua to extreme eastern Panama, and on the Pacific slopes from the Osa Peninsula, Costa Rica to Colombia (Guyer and Donnelly 2005). It lives in lowlands, primarily rainforest (Caldwell and Summers 2003). It is a shy species, found deep in the forest interior (Leenders 2001).

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Physical Description

Morphology

Dendrobates auratus has many color variants. Most of them are black and either green or light blue, with the black in bands or spots. The Hawaiian frogs are metallic green or brownish-black. The adults are approximately 4 cm long. As is true of most frogs, adults have a fused head and trunk with no tail. Tadpoles use gills to breathe, unlike the adults, which breathe through lungs. Tadpoles also lack legs and have tails, which is appropriate for their watery habitat. Another important physical characteristic of D. auratus is the poison glands located throughout the surface of their body. Their bright colors are believed to encourage predators with color vision to avoid the frogs. The boldly contrasting patterns may be aposematic to predators that lack color vision, although this has not been proven. Approximately 90 alkaloids have been identified from all species of dendrobatids <.. (Myers & Daly, 1976)

Diagnostic Description

Identification

Adult

Dorsal

The dorsum is brown or black with bright green, blue, yellow or cream-colored markings (including spots, stripes, bands, blotches). Birkhahn et al (1994), Gray (2000), and Patrick and Sasa (2009) describe color and pattern variation in this species. Gray (2000) suggested that the bright coloration is important in visual communication in this species, rather than functioning as aposematic coloration.

Eye

The iris is black.

Extremities

Hands and feet have no webbing. Fingers and toes have small discs at the tips.

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Ecology

Habitat

Dendrobates auratus adults are found on the floor of rain forests. They prefer locations near small streams or pools. The tadpoles live in these small pools or streams. Where the frogs live in the heavily populated areas of Hawaii, the eggs are often deposited in broken beer bottles or old cans instead of the usual puddle. (Whitfield 1984)

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Habitat and Ecology

It is an arboreal and terrestrial diurnal species of humid lowland and submontane forest. It is also found in dense secondary growth and cocoa plantations (Kitasako, 1967). The adults are often associated large buttressed trees. Males are essentially non-territorial, but occasionally engage in aggressive competition (Wells, 1978). The species is polygynous; females actively compete for males and attempt to guard their mate from others. The species shows a high degree of paternal care. After oviposition upon leaf-litter the male guards and cares for the clutch of three to 13 eggs (Silverstone, 1975; Schafer, 1981; Heselhaus, 1992). On hatching (13-16 days in captivity) the tadpoles are carried by the male to a stagnant water body in a tree-hole, the leaf axil of a bromeliad (up to 30m from the forest floor), or a small ground pool (Eaton, 1941; van Wijngaarden, 1990). Wild tadpoles feed on protozoans and rotifers, and metamorphose after 39-89 days; in captivity, sexual maturity is attained at between six and 15 months (Eaton, 1941; Silverstone, 1975; Summers, 1990; Zimmermann and Zimmermann, 1994). A reduction in the number of egg clutches and tadpoles maintained by the male results in a more rapid development of the eggs and higher growth rate of tadpoles (Wells, 1978; Summers, 1990). Longevity of at least six years reported in captivity (Zimmermann and Zimmermann, 1994).

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Comments: An arboreal and terrestrial diurnal species of humid lowland and montane forest; also found in dense secondary growth and cocoa plantations (Kitasako, 1967. Adults are often associated large buttressed trees. Males are essentially non-territorial, but occasionally engage in aggressive competition (Wells, 1978). D. auratus is polygynous; females actively compete for males and attempt to guard their mate from others. The species shows a high degree of paternal care. After oviposition upon leaf litter the male guards and cares for the clutch of three to 13 eggs (Silverstone, 1975; Schafer, 1981; Heselhaus, 1992). On hatching (13 to 16 days in captivity) the tadpoles are carried by the male to a stagnant waterbody in a tree-hole, the leaf axil of a bromeliad (up to 30 m from the forest floor), or a small ground pool (Eaton, 1941; van Wijngaarden, 1990) Wild tadpoles feed on protozoans and rotifers, and metamorphose after 39 to 89 days; in captivity, sexual maturity is attained at between six and 15 months (Eaton, 1941; Silverstone, 1975; Summers, 1990; Zimmermann and Zimmermann, 1994). A reduction in the number of egg clutches and tadpoles maintained by the male results in a more rapid development of the eggs and higher growth rate of tadpoles (Wells, 1978; Summers, 1990). Longevity of at least six years reported in captivity (Zimmermann and Zimmermann, 1994). In Hawaii: well-foliated moist valleys; usually in moist places; on ground and in bushes. Usually under shelter late spring - early fall. Sometimes observed in standing water (rain-filled debris, depression in rock). Eggs are deposited in moist places on land, transported on dorsum of male to standing water (usually a small water-filled cavity) where development is completed.

Habitat

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Dendrobates auratus individuals prey on small invertebrates. Most notably, these frogs eat ants that have high quantities of alkaloids in their tissues. The frogs can sequester those alkaloids in their skin, which is what makes them poisonous. Dendrobates auratus individuals kept in captivity and fed a diet of insects without alkaloids will lose their toxicity. These frogs capture their prey by using their sticky, retractible tongues as well as their excellent eyesight. (Obst 1988)

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General Ecology

Ecology

Ecology

This species is active during the day (Dunn 1941, Ibanez et al 1999). Predators of adult D. auratus include motmots (Master 1999) and theroposid spiders (Gray 2000). Tadpoles are consumed by grapsid crabs (Gray and Christy 2000).

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Life History and Behavior

Behavior

Little is known of communication in this species. Males use vocalizations to attract females for mating and advertise territories. It is also possible that visual displays, tactile stimuli, and chemical cues are involved. They use their excellent vision to capture prey.

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Behaviour

Call

A quiet buzzing sound (Dunn 1941, Ibanez et al 1999, Savage 2002).

Behavior and communication

Males actively defend territories (Savage 2002). Because male availability is limited when they are caring for clutches, females often compete for males, wrestling away other females (Savage 2002). Likewise, females generally take the leading role during courtship, although both males and females have been observed to hop around and touch the other sex (Wells 1978).

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Life History

Breeding season

Breeding occurs throughout the rainy season (Ibanez et al 1999). Wells (1978) provides a description of some courtship behavior. A male was seen calling and courting a female in Cerro Chucanti during the dry season (in March 2010; Hughey and Touchon, pers. obs.).

Egg

Eggs are laid in the leaf litter and cared for by males (Summers 1989). Clutches are very small (Savage 2002), and may contain just two eggs (Dunn 1941). Upon hatching, tadpoles are carried by the males to small bodies of water (e.g. bromeliads or tree holes), where they develop (Eaton 1941).

Tadpole

Tadpoles are medium-sized and black (Savage 2002, Eaton 1941). The body is oval-shaped with a longish tail with small tail fins (Savage 2002). Tadpoles cannibalize other individuals, but also consume aquatic invertebrates present in phytotelmata (Caldwell and Arajuo 1998, Fincke 1999).

Metamorph juvenile

Metamorphosis can take as long as 43 days (Dunn 1941, Eaton 1941). Froglets develop green coloration almost immediatedly after metamorphosis (Pope 1941, Eaton 1941).

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Reproduction

Male frogs go through an elaborate ritual to attract mates. The male first fight among themselves to establish territories, which are then fixed for the remainder of the mating season. The male then attracts a female with vocalizations consisting of trilling sounds. Part of mating behavior involves the frogs rubbing against each other.

Mating System: polygynous

Once the courtship ritual is completed, the female lays up to six eggs in a small pool of water. The eggs are encased in a gelatinous substance for protection. The mating season of D. auratus occurs throughout the entire rainy season of the rain forest, from mid-July through mid-September.

Breeding interval: Breeding may occur more than once yearly.

Breeding season: Reproduction occurs during the rainy season, July to September.

During the two week development period, the male returns to the eggs periodically to check on them. Once the tadpoles hatch, they climb onto the males back and he carries them to a place suitable for further development, such as a lake or a stream. For the duration of this trip, the tadpoles are attached to the males back by a mucus secretion, which is soluble only in water so that there is no chance of them accidentally falling off. Once they are at their final destination, the tadpoles are on their own. They take an additional six weeks to develop into adult frogs. (Mattison 1987)

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Conservation

Conservation Status

Dendrobates auratus are not currently listed as in danger. However, with the destruction of their habitat, tropical rain forests, it is now likely that in a short time they will be in trouble. In fact, it is speculated that members of the genus Dendrobates will be the first poison dart frogs to be put on the endanged list of a major conservation organization such as CITES or ESA.

Listed as Least Concern in view of its wide distribution, tolerance of a degree of habitat modification, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

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Trends

Population

This is an abundant species that is often seen and regularly recorded throughout its range. There is great geographic variation in the appearance of this species; over 15 distinct colour morphs of wild D. auratus have been recorded. (Heselhaus, 1992). The blue morph of D. auratus present on the Pacific side of Panama is believed to be threatened with extinction (Heselhaus, 1992).

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Life History, Abundance, Activity, and Special Behaviors

These frogs forage during the day (Guyer and Donnelly 2005). They move by a series of hops, stopping briefly and hopping again when disturbed. They are excellent climbers with individuals climbing to 45 m above the ground (Savage 2002).

Males are territorial at high population densities but may not be at low populaton densities (Caldwell and Summers 2003). The male call is a high-pitched, insect-like buzz sounding like "cheez-cheez-cheez" (Leenders 2001). The call averages 3.5 kHz in frequency, and can last from two to four seconds followed by a five-second pause (Savage 2002). Males can mate with many females and care for offspring of different females simultaneously (Caldwell and Summers 2003). Females court the males and wrestle other females and chase them from their territories (Savage 2002). This behavior increases male reproductive success but puts survival success of offspring in jeopardy, since females do not defend their territories (Caldwell and Summers 2003). A single male can mate with up to six females (Savage 2002). After being selected by the females, the males then lead the females to the nest site made from leaf litter and the females lay four to six eggs there (Guyer and Donnelly 2005). The male visits the eggs periodically over the incubation period to shed water, remove fungus, and rotate the eggs. After the eggs hatch, the tadpoles crawl up on the male's back (Savage 2002). The male then transports the tadpoles to small pools of water, usually found in tree holes (Caldwell and Summers 2003). If some eggs hatch earlier than others, the tadpoles that are born first may practice cannibalism by eating the smaller tadpoles.

The tadpoles' diet consist of algae, detritus, protozoans, insect larvae, and each other (Leenders 2001). Tadpoles are moderate-sized and can reach 30 mm (Savage, 2002). The adults' diets consist mainly of tiny ants and mites but they also prey on beetles, flies, and springtails (Caldwell and Summers 2003). They are known to have a life-span of eight years in captivity but it is much lower in the wild (Leenders 2001).

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Threats

There is a general loss of suitably wooded areas and collection for the international pet trade. Owing to the apparently low fecundity of this species, the possibility exists that over harvesting, especially in the more rare morphs, might contribute to localized population declines. Approximately 18,500 specimens of D. auratus were reported in trade over the period 1991 to 1996. The great majority of specimens were live animals, exported from Nicaragua, and presumably destined for the herpetological pet market. The USA was by far the largest single importer of D. auratus (about 15,000 animals in total) during this period. It is believed that the trade in Nicaragua was decreasing by 2002 because of over collection. McKeown (1996) states that populations on Oahu are highly sensitive to destruction of their habitat and over collection. Museum specimens of this species have been found to have chytrid fungi, the current impact of this pathogen on D. auratus is not known.

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Comments: General loss of suitably wooded areas and collection for the international pet trade. Owing to the apparently low fecundity of this species, the possibility exists that overharvesting, especially of the rarer morphs, may contribute to localised population declines. Approximately 18,500 specimens of D. auratus were reported in trade over the period 1991 to 1996. The great majority of specimens were live animals, exported from Nicaragua, and presumably destined for the herpetological pet market. The USA was by far the largest single importer of D. auratus (~15,000 animals in total) during this period. It is believed that the trade in Nicaragua was decreasing in 2002 because of overcollection (GAA workshop). McKeown (1996) states that populations on Oahu are highly sensitive to destruction of their habitat and overcollection. Museum specimens of this species have been found to have chytrid fungi, the current impact of this pathogen on D. auratus is not known.

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Management

Conservation Actions

This species is listed on Appendix II of CITES, and the species occurs within many protected areas. Within Colombia, Decree INDERENA No. 39 of 9 July, 1985, forbids the collection of Dendrobates spp. from the wild for breeding (or other) purposes. Nicaragua has established CITES export quotas for this species.

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Dendrobates auratus have long been used by local peoples to provide poison for their weapons. Currently the possibility of various medicines being derived from the frogs is being explored. Pharmaceutical companies are investigating the possibilities of a painkiller, ABT-594, being developd from a compound called epibatidine, which is found in D. auratus. The drug has the potential to be approximately 200 times more potent than morphine in blocking pain in animals, yet shows no sign of side effects of addiction. Since there have been over 80 alkaloids discovered from the 20 species of dendrobatids, there is much more research being conducted, especially on the effects of the alkaloids on neurological and muscular disorders. These frogs are also bred in captivity and sold extensively in the exotic pet trade. People enjoy them as pets because they are so colorful, and although they provide a challenge to owners, they do fairly well in captivity. (Merickel 1998)

Contents

The green-and-black poison frog, while not the most toxic poison dart frog, is still a highly toxic animal. The very small amount of poison the frog possesses is still enough to make a human heart stop beating. Like most poison dart frogs, however, the green-and-black poison dart frog will only release its poison if it feels that it is threatened, and wild specimens can be handled if the human holding it is calm and relaxed. The green-and-black poison frog, as with all poison dart frogs, loses its toxicity in captivity due to a change in diet. This has led scientists to believe that the green-and-black poison frog actually takes its poison from the mites it feeds on.[2]

The mint poison frog is in all ways an average poison dart frog. Males reach about 0.75 inch long; females are slightly larger, up to an inch long or bigger. As the common name "mint poison dart frog" suggests, the green-and-black poison frog typically has mint-green coloration; however, they can also be forest, lime, emerald green, turquoise, pale yellow, or even cobalt blue. Many also have splotches of dark colors, ranging from wood brown to black. The green-and-black poison frog is one of the most variable of all poison frogs in appearance. Some have black or brown splotches, others are dappled, or have "splashes" of black, like Oophaga sylvaticus.

D. auratus is semiarboreal, hunting, courting, and sleeping in the trees, but as it is a small frog, it cannot jump far enough to span the distances between trees, so it returns to the ground to travel. To assist in climbing, the mint poison dart frog has small, sucker-like discs on the ends of its toes, which create a slight suction as the frogs climb, making their grip mildly adhesive (although some individuals do have difficulty climbing).

Like all poison dart frogs, green-and-black poison dart frogs gather in large groups before mating. They squabble over territories; eventually each individual male frog clears a small patch for himself. Females wander among the males, the latter then attempt to impress the former with their bird-like mating calls. Once a male has caught the attention of a female, he leads her to a site he has selected for egg deposition. The female lays her eggs, which he then fertilizes. In approximately 14 days, these hatch into tadpoles.[3] Their parents (typically the male) then carry the tadpoles into the canopy, with the tadpoles sticking to the mucus on their parents' backs. The parents then deposit their tadpoles into the small pools of water that accumulate in the center of bromeliads, and guard the tadpoles while they feed on algae and small invertebrates that inhabit the tiny pool.

Green-and-black poison dart frogs are popular exotic pets due to their small size, bright colors, and intriguing behavior. As with all frogs, they have permeable skin and should not be handled whenever possible. If it is imperative to move them, handling should be done with extreme care and with clean hands. Their small size makes them fearful of animals much larger than themselves, such as humans, and will attempt to escape if handled. To prevent escape, many frog keepers move their amphibians in fine-meshed nets or with cupped hands. A partly terrestrial, partly arboreal enclosure should also be provided.Poison dart frogs may be small, but is very active and needs a suitably large terrarium (usually 100 x 60 x 60 centimeters) with a high level of humidity. Live plants should also be added to provide hiding places, and bromeliads in the event the frogs breed.